Mint 6 worked perfectly with my HD 4670. Mint 7 will not post any video with an HD 4670. It works fine with an HD 4830 which takes the same windows driver.
I switched to an old 7900GS and Mint 7 works fine. Also tried a 9600GSO 768MB and it works fine also.
Ubuntu 9.04 won't work with the HD 4670 as well.
I love MInt, but if a device doesn't work correctly I am clueless on how to fix it.
I also have an old HD 3850 that I will try, but I really want the low power 4670 to work!